Speed-regulating device for prime movers



.srEED REGULATING; DEV FOR PRIME rvn'gv Eirs May 27, 1930.

. Filed July 14, 192'? 4/ r, /A4 I! ME...

Patented May 27, s 1930 UNITED STATES OFFICE A BERT Lt'r'rEr, or ZURICH, SWITZER AND, assrenoa ro THE FIRM AKTIENGESELL- sonar'r DER MASGI-IINENFABRIKEN ESGI-IER wYss & cm, or zuaron, swrrznn- LAND SPEED-REGULATING DEVICE FOR PRIME MOVERS Application filed July 14;, 1927, Serial No. 205,729, and in Switzerland July 17, 1926.

Speed regulating devices, or governors, for prime movers are already known in which two" gear pumps are used for supplying auxiliaryfluid pressure media. Such adevice is illustrated in Fig. 1 of the accompanying drawings, in which figure the numeral 1 designates one of these two pumps. This pump 1 is driven by the prime mover designed as a steam turbine 30 the rota-ryspeed of which it is desired to regulate through a worm gearing 31, and consequently said pump partakes of the speed fluctuations of the machine 30. The pump 1 which is connected to a reservoir 38 containing a liquid forces liquid under pressure through a diaphragm 2, in front of which the speed fluctuations" of the pump 1 manifest themselves in the form of fluctuations of pressure. These pressure fluctuationsIact upon a plunger l which is under the influence of a tension spring 5 and to which is also, secured a fluid tightdiaphragm 6. The second pump is indicated in Figure 1 of the drawings by the numeral 7 it is driven by the steam turbine 30 through a worm-gearing 32 and supplies liquid under pressure from the reservoir 33 to a pressure chamber 8. This latter is provided with a vent or nozzle opening 9 which is so controlled by the plunger 4: that when the pressure rises in front of the diaphragm 2, that is to say, when the pressure in receiving-chamber 10 increases, the auxiliary liquid delivered by the pump 7 can escape more readily through the said opening 9, so that the pressurein the chamber 8 falls when the rotary speed of the prime mover to be governed increases. The pressure chamber 8 is in permanent connection with a space 12 above a piston 11 containedinwa cylinder 11 and upon the underside of which piston acts, a constant pressure prevailing behind diaphragm 2 in the discharging chamber 21, whichis either open to atmospheric pressure or connected to the lubricating system of the prime mover, and also a spring 13. The lower space of the cylinder 11 discharges into the chamber. 21. The piston 11 is operatively connected to the speed regulating member proper 34 (e. g. an

inlet valve) ofthe turbine 30 the speed of which is to be governed. I

If the speed of the turbine 30 drops by reason of increased load, the pumps 7 and 1 discharge lessliquid to their chambers 8 and 10.

If first the operation of pump 7 be considered, the pressure in chamber 8 will decrease and the pressure on the upper surface of the piston 4 will be reduced and the spring 5 will lift the piston 4 until the pressure in chamber 8 is substantially the same as it was before the reduction of speed of the turbine.

Pump 1 also reduces the pressure in chamber 10 so that the spring 5, by reason of the reduction of pressure on piston 4, will draw tllle Episton still further to the opening in nozz e. 1

s A screw14; which enables the tension of the spring 5 to be increased or decreased provides for adjustment of the number of revolutions per minute to the desired value. H s

It is the object of the present invention, in a speed governing device of the kind above described, to eliminate one of the two pumps which supply auxiliary pressure fluid. To this end, according to the invention, a part of the pressure fluid which is delivered by the pump, which rotates at a speed proportional to that ofthe machine to be governed flows through an auxiliary throttle device to the pressure chamber the fluid pressure in which determines the setting of the regulating member proper of the machine. i

Constructions of governor devices in accordance with the present invention are illustrated somewhat diagrammatically and by way of example in the accompanying drawings, in whichi i jFig. 2 shows one constructional form of fi ig. 4 shows a second embodiment and governor device according to the invention.

Fig. 5 a third embodiment of the invention.

The device illustrated in Fig. 2 is differentiated from that shown in Fig. l by the fact that it includes no pump such as the pump 7 and, further, by the fact that the receiving chamber 10, which is fed b the pump 1 driven by the machine 30 to e governed, is connected to the pressure chamber 8 by a duct 15 in which is fitted a diaphragm 16 serving as an auxiliary throttling device. In other respects the device is made exactly the same as the known speed governing device above described.

The graphs in Figure 3 show on a rectangular system of co-ordinates the relation between the pressure in receiving chamber 10 and the pressure p in chamber 8, in a H function of the number n of revolutions per minute of the prime mover to be governed. At low values of n the plunger 4 first closes the nozzle opening 9 and then p and 19 increase equally, so that 2 17 This condition is shown in curve (band it persists until the pressures p and p acting on the plunger 4, overcome the spring 5, as at the pointP in Fig. 3. Pressure fluid then flows not only through the diaphragm 2 but also through the nozzle opening 9. Rise of the pressure 12 is thus slowed down, as is apparent from curve I) of Fig. 3 and the pressure 12 upon increase of the number n of revolutions per minute, falls oflf' from the point P as indi cated by curve 0. The points P and P of the curve 0 correspond to the pressures 2 which prevail in'the lowest and in the highest positions of the piston 11 respectively. From the projections P and P on to the 'n-axis of the system of co-ordinates the speed fluctuations of the governed machine between no load and full load can be ascertained. Given the distances of the points P and P from the n-axis, the constant cyclic irregularity becomes greater the flatter the curve 0 runs. Moreover, if the point P be given, the relation of the diaphragm 2 to the diaphragm 16 determines the steepness of the curve 0. A very steep curve is obtained if the diaphragm 16 be small in relation to the diaphragm 2.

Another way of increasing the steepness of the curve 0 is shown in the construction illustrated in Fig. 4, wherein the plunger 4 is provided with a bore 17 connecting the pressure chamber 8 with another chamber 18 beneath the said plunger. The fluid pressure p, prevailing in the chambers 8 and 18 gives an upwardly acting resultant, since that end of the plunger which projects into the chamber 18 presents a surface 18 of greater area than that of the opposite end of the plunger which confronts the nozzle '9. A further noteworthy peculiarity of the construction according to Fig. 4 resides in the fact that the diaphragm 2 of Fig. 2 is replaced by an annular gap 20, formed between Q2 P2 (Pl 1 2) The pressure in discharging chamber 21 is assumed to be negligibly small. If f be the effective surface of the flange 19 on the plunger 4 upon which the pressure p acts, and if f be the end surface area of the and plunger exposed to pressure in the chamber.

18, less the surface of the nozzle 9, (i. e. the effective surface subjected to the pressure p it can be proved that for any desired couple of values 79 p the plunger 4 is in stable equilibrium when Taking into account the most unfavorable case in which 17 0, this gives the following practical formula for the formation of the member 4:

- If particularly f be made so extremely small as to be negligible the choice of the ratio 8 need not be restricted in any way.

It can be proved, that in the construction according to Fig. 4 with the same diaphragm or ratio, the curve 0 may be made to fall off more steeply than in the construction according to Fig. 2.

Fig. 5 illustrates a form of construction wherein, for the purpose of reducing friction, an oscillating lever 4 is substituted for the plunger 4, the said lever penetrating the partition wall 25 between the receiving chamber 10 and the pressure chamber 8. This lever 4 carries a plate 23 surrounded by an annular gap 20 and also a small plate 24 adapted to cooperate with a vent or nozzle opening 9; further the said lever is biased by a tension spring 5. The manner in which the device according to Fig. 5 operates is the same as in the case of the device according to Fig. 4. In particular the same conditions for stability obtain.

to said piston and having a vent therefrom,

means of constant area to throttle the flow from said receiving chamber to said pressure chamber, means to control the venting of liquid from the pressure chamber, and means to throttle liquid by-passing the pressure chamber and liquid flowing from the receiving chamber into the discharging chamber, the means to control the venting of liquid from the pressure chamber being moved by the difl'erential liquid pressure between the receiving chamber and the discharging chamber.

2. A device for governing the speed of prime movers provided with a regulating member; comprising a liquid pump constantly driven by the machine to be governed, a receiving chamberinto which said pump constantly delivers a quantity of pressure liquid varying in dependence of the speed of said machine, a piston by which the regulating member is moved, a cylinder containing said piston, a discharging chamber into which liquid from said cylinder dis charges, a pressure chamber from which liquid is supplied to said cylinder above the piston and having a vent therefrom, a dia phragm having a constant area opening for throttling the liquid passing from the receiving chamber to the pressure chamber, a valve to control said vent, andmeans to throttle liquid by-passing the pressure chamber and liquid flowing from the receiving chamber, the means to control said vent being moved by the differential liquid pressure between the receiving chamber and the discharging chamber.

3. A device for governing the speed of prime movers provided with a speed regulating member; comprising a pump which partakes in the speed fluctuations of the machine to be governed and constantly delivers a quantity of pressure liquid varying in dependence on the speed of the machine, a

with a nozzle confronting one end of said movable member, means formed integral with said movable member to throttle liquid bypassing the pressure chamber, and means adapted to act on the speed regulating member of the prime mover in dependency of the liquid pressure prevailing in said pressure chamber, said movable member being pro-.

vided with a bore extending from one of its ends to the opposite end, the surface area of the end confronting the nozzle of the pressure chamber being smaller than the surface area of its other end, so that the liquid pressure acting on said two ends of the movable member gives a resultant force moving said member in a direction such as to tend to close said nozzle.

4:. A device for governing the speed of prime movers provided with a speed regulating member; comprising a pump which partakes in the speed fluctuations of the machine to be governed and constantly delivers a quantity of pressure liquid varying in dependence on the speed of the machine, a throttling device through which is forced a part of the pressure fluid delivered by said pump, a movable member acted upon by the pressure prevailing in front of said throttling device, a casing enclosing said movable member, a flange on the movable member forming together with a part of said casing a gap which functions as a throttling device for a part of the pressure fluid delivered by said pump, a pressure chamber provided with a nozzle confronting one end of said movable member, and means adapted to act on the speed regulating member of the prime mover in dependency of the liquid pressure prevailing in said pressure chamber, said movable member being provided with a bore extending from one of its ends to the opposite end and the surface area of the end confronting the nozzle of the pressure chamber being smaller than the surface area of its other end, so that the liquid pressure acting on said two ends of the movable member gives a resultant force moving said member in a direction such as to tend to close said nozzle.

In testimony whereof, I havesigned my name to this specification.

ALBERT LUTHI. 

